Metal silicide thin films are integral parts of all semiconductor devices. They have been used as ohmic contacts, gate electrodes, local interconnects, and diffusion barriers. The many requirements of the metal silicide films include low resistivity, good adhesion to silicon, low contact resistance to silicon, appropriate Schottky or Ohmic barrier height with heavily doped silicon (n+ or p+), thermal stability, appropriate morphology for subsequent lithography and etching, high corrosion resistance, oxidation resistance, good adhesion to and minimal reaction with SiO2, low interface stress, compatibility with other processing steps such as lithography and etching, minimized metal penetration, high electromigration resistance, and formability at low temperature. Metal silicides that have received the most use attention as metal contacts for advanced devices are TiSi2, CoSi2, and NiSi.
As feature dimensions are continuously reduced, new methods and materials are needed for contacts, including contacts with minimum dimensions of about 10 nm and smaller, and for germanium (Ge)-containing devices.